high and the pressure heavy is to place these pumps in series, the second taking its supply water from the first, and so starting its work with a considerable degree of pressure; the third pump taking water from the second, and so on. As many as 10 of these turbines may be thus combined to form the "ten-stage» turbine pump. By this means the load is distributed, the velocities of the rotors being transmuted into pressure in the diffusing chambers. These multi-stage turbine pumps are used in the equipment of fire-boats, which are required to deliver great volumes of water at high pres sure. The injector and the pulsometer are also classified as pumps, though operating on prin steam from the chamber (a) and admittting it to the chamber (b), from which the water is gradually forced out. In the meantime the condensation of the steam in the chamber (a) creates a partial vacuum, and the pressure of the atmosphere on the external water forces it through the valve (f) into the chamber, so that when it is nearly full, the air it contains will be sufficiently compressed to force the valve (d) over to the right, thus producing a continuous action. The efficiency of pulsometers is equal to that of small direct-acting feed pumps, and they are extensively used on account of their simple construction and great durability. Nearly allied to the injector and pulsometer in point of the physical action involved is the "explosion," or "internal combustion" pump a typical example of which is the so-called Humphrey gas pump. It consists of a chamber a k TAM e g FIG. 8.-Sectional View of Pulsometer. ciples quite different from those exhibited in the machines more familiarly known under the title of "pump." The injector is described in detail in a special article (see INJECTOR). The pulsometer consists of two bottle-shaped chambers (a) and (b), the tapering necks of which incline toward each other in a common passage at (c). At the lower end of this passage is a valve (d), which when moved slightly will simultaneously close the opening of the neck of one chamber, and open that of the other. Water is admitted into the chambers through the passage (e), and valves (f) (g) and forced out through the valves (h) (i), and passage (j) into the air chamber (k). The device operates as follows: Suppose both chambers are full of water and the valve (d) to the right. When steam is admitted to the chamber (a) the water is forced out by direct pressure through the valve (h) into the air chamber (k), so that when the chamber (a) is nearly or quite empty, the valve (d) moves to the left, cutting off the FIG. 9.-Sectional Diagram of Double-cylindered "Humphrey" Type of Gas Pump. (A) in which an explosive mixture of air and vaporized gasoline is admitted through the valve (V). This mixture is exploded by an electric spark, and the expanding gases press downward upon the water in the chamber (B). forcing it out through the pipe-line (P), and into the reservoir (R) and up the standpipe (D). When the force of the gas has expended itself the escape valve (E) drops in the reduced pressure, and the burned gases pass out before the return surge of the water standing in the standpipe (D). Meanwhile, in the low pressure prevailing, the inlet valves (I) open and admit water from the basin (K), which pours into chamber (B) until the returning water from the pipe-line brings pressure enough to close them, and also the exhaust valve (E), and opens the gas valve (V) by a float. A backward surge of the water, in coming to an equilibrium, sucks in a charge of gas through (G), and the vibrating water comes back once more and compresses the gas, at which juncture it is fired; and the cycle is repeated indefinitely. It will be seen that one delivery of water covers four vibrations in the pump. This leisurely action has been reduced to half the time by connecting two pairs of chambers to the suction pipe, so that the first resurge after firing compresses the gas charge in the second gas chamber, and fires it, each resurge thus being sent forward as a discharge. The largest of these gas pumps in America is a 66-inch pump in irrigation service at Del Rio, Texas, delivering 28,000 gallons per minute at a height of 38 feet. "Impulse pumps" are those operated by the impact of a falling column of water or by the force of a moving column of water suddenly arrested, or by jets of steam, compressed air, PUMPS AND PUMPING MACHINERY or water under high pressure. The hydraulic ram is an example of the first group. It was originally designed by Whitehurst, a watchmaker of Derby, England, in 1772, and subsequently perfected by Montgolfier, the famous French balloonist, in 1796. It consists of a supply pipe (a); an air-chamber (b) attached to the upper side of the pipe (a), and fitted with a valve (c) at the pipe opening; a valve (d) at the end of the supply pipe, and a vertical pipe (e), opening freely into the air-chamber, through which the water is raised to the desired elevation. The device operates as follows: The valve (d) is made just heavy enough to drop and open the lower end of the pipe (a) when the water filling the pipe is at rest. Now assume that this valve opens, allowing the water in (a) to run out. This water gradually acquires an increasing momentum, which finally carries the valve up against its seat and closes the outlet. The water in FIG. 10. Sectional View of Hydraulic Ram. (a) is thus brought suddenly to a state of rest and a part of it rushes into the air-chamber (b) through the valve (c). But, the instant the water in (a) is again in a state of rest, the valve (d) drops again, opens the outlet, allows the water to run out, and is again closed when the increasing pressure is strong enough, bringing the water again to a sudden halt and forcing some more of it into the air-chamber, thence by the elasticity of the air cushion (b) to be pushed upward through the pipe (e) to the point of delivery - and thus the cycle is continued. The action of the valve (c) prevents the return of the water from the airchamber to the pipe (a). This device is adapted to numerous locations and will operate automatically and continuously, without any attention whatever, so long as the surface of the water at the source of supply is kept at the same elevation so as to insure a uniform pressure against the valve (d). When the perpendicular distance from the source of supply to the valve (d) is small, and the water is required to be raised to a comparatively great height, pipe (a) must not only have a considerable fall but must be of larger diameter, and be of sufficient length to prevent the water from being thrown back into the source of supply by the shock when the valve (d) closes. It is also necessary to maintain the supply of air in the air-chamber, which in time, under the great pressure, becomes depleted by being dissolved in the water. In small rams a sufficient amount of air enters through the valve (d), but in rams of considerable size a small snifting valve," attached to another chamber immediately below the air chamber, automatically supplies the additional air whenever it is necessary. Jet pumps operating with steam or compressed air are termed "ejectors." They are in use for spraying or atomizing liquids in 9 various manufacturing processes. The jet pumps operating with high pressure water are known commercially also as "eductors." They have no valves or other moving parts, and are not subject to wear and tear, and, being also of low first cost, are very economical where a small supply of high-pressure water can be commanded. The construction is extremely simple. The high-pressure pipe is placed in the centre axially of a larger flow or discharge pipe and fitted with a conical mouthpiece. The discharge pipe is narrowed at the opening of the jet and then expanded gradually to its full size. With a three-inch discharge pipe and a one and one-half-inch jet pipe operating with a pressure of 40 pounds to the square inch (about 90 feet head) the discharge will amount to 5,000 gallons per hour. For lifting water the pressure in pounds per square inch of the jet opening is made two and one-half times the elevation in feet. Thus if the lift is 20 feet the pressure required is 50 pounds. The eductor works well on the level of discharge if the suction lift is not more than 15 feet. The so-called "high-duty" pumps are those in use for heavy work against great pressure. They include waterworks pumps, mine pumps, fire-service pumps, elevator pumps, hydraulic pressure pumps and the like. Practically all are direct-acting pumps operated by steam. They are built both in the horizontal and upright forms. One of the first American pumps designed for high-duty waterworks service was the "Worthington direct-acting duplex steam pump." It consists of two double-acting plunger pumps placed side by side with the piston-rod of each steam cylinder connected by a lever to the slide valve of the adjoining steam cylinder, so that the movement of each piston instead of operating its own slide valve, as in the simplex pump, operates the slide valve of the adjoining cylinder. The valve motion is so adjusted that just before the piston of one cylinder has finished its stroke, the piston of the other begins its movement. The load of the water column is then taken up alternately and produces a steady flow without serious strains, harshness of motion and noise, which characterize the action of the simplex pumps, in which the water column is started into motion at the beginning, and arrested at the end of each stroke of the piston. Although the simplicity of their mechanism, together with the cheapness of their first cost and the certainty of their action, placed them at the head of all the machines of their class, when considered from a mechanical standpoint, the loss of economy in the use of steam continued to militate against their general use for heavy duty purposes. Their light weight prevented the cutting off of the steam in the steam cylinder so as to complete the stroke of the piston by the aid of the expansive energy of the steam thus cut off. Therefore the steam applied to move the pistons had to be applied in sufficient quantity and pressure to overcome the weight of the water column and its friction through the pump and connections, at the very beginning of the stroke, and maintained without diminution throughout the stroke, up to its termination, since a falling off in either volume or pressure during any part of the stroke would have stopped the action of the pump instantly. This defect, however, was completely eliminated by applying to them the principle of multiple expansion in the use of steam in compound condensing steam engines. Another steam cylinder was added to the end of the one already in use, and placed in a direct line with it so that the high pressure steam admitted to the first and smaller cylinder, after moving its piston, was exhausted behind the piston of the large cylinder upon its return stroke. Still further economy was produced in the larger compound engines by using a condenser to create a vacuum in the large steam cylinder, thus bringing the efficiency fully up to that of the best high-duty rotative engines of the most important pump rod which is extended for this purpose through the outer end of the pump chamber. On the end of this rod is fastened a cross-head which moves in guides attached to the outer end of the pump. On this cross-head, and situated opposite to each other, are two hemispherical recesses. On the guide plates are two journal boxes, one above and the other below the plunger-rod, equidistant from it, and placed at a point equal to the half stroke of the cross-head. Each journal box carries a short cylinder hung on trunnions, which allow the cylinder to swing in unison with the motion of the plunger rod. In these cylinders are plungers or rams, which pass through a stuff Ewordt FIG. 11.-Sectional View of Worthington High Duty Pumping Engine. ing plants of the world with yearly records ranging from a duty of 50,000,000 to 120,000,000 foot-pounds per 100 pounds of good coal. The duty of the Worthington pumping engines was still further increased, and the entire arrangement, from the power-producing to the pumping ends, was made to represent the highest perfection of modern pumping machinery, by the application of the accumulator, a device originally invented by J. D. Davis, in 1879, and perfected by C. C. Worthington, in 1884. With it the steam may be cut off in the steam cylinder soon after the beginning of the piston stroke, a part of the power being stored and brought into play toward the end of the stroke so that the force exerted upon the pump plunger remains uniform through the entire stroke. In a compound direct-acting steam pump, the device is attached to the plunger ing box on the end. The outer ends of the rams have rounded projections which fit into the recesses on the cross-head, which is moved in and out with the plunger, thus tilting the cylinders backward and forward. These cylinders are called "compensating cylinders." When the engines are used for pumping water, they are filled with water, and when used for pumping oil, they are filled with oil. The pressure on their rams is produced by connecting the cylinders through their trunnions which are hollow, with an accumulator, carrying a ram which moves up and down as the rams of the cylinder move in and out. This accumulator is of the differential type, the small lower cylinder of which is filled with water or oil, in which the ram moves, while the larger upper cylinder is filled with air. On the top of the accumulator-ram is a large piston-head which Views of Large V.T.E. Pumping Engines installed for City of Cleveland, Ohio, by Allis-Chalmers Manufacturing Company |